The present invention relates generally to welding-type systems and, more particularly, to a system and method for calibrating wire feeder motors for improved starting and consumable delivery.
Performance demands on wire feeders and torches not only require accurate speed but also starting, acceleration, deceleration, and brake/braking control. That is, the consumable wire must be accurately controlled when starting a welding process and accurately disengaged upon termination of the welding-type process. Failure to accurately control startup and delivery of the consumable wire can result in excessive spatter, build-up on the tip of the wire, and generally less accurate welding.
Typical wire feeders have a driven roller assembly for driving a consumable metal wire from a feed spindle through a welding gun for introduction to a weld. The drive mechanism in these driven roller assemblies typically includes a motor or combination of motors. Operation of the motor or motors is typically directed by a motor control system including a controller or processor. In particular, the wire feed control system typically includes a fast acting back electromotive force (EMF) control loop and a slower tachometer feedback control loop. The controller uses feedback from the feedback loops to control the motor or motors based on a stored set of general calibration parameters of the motor.
Each feedback loop is designed to provide feedback regarding a particular phase of the welding-type process. That is, the back EMF control loop is generally designed to respond to instantaneous load changes and the tachometer feedback loop generally provides feedback regarding average wire feed speed. As such, the back EMF control loop is utilized during periods requiring fast responses to changing conditions while the tachometer feedback loop is designed to be utilized during stabilized conditions.
For example, during startup of the wire feeder motor, the controller utilizes feedback from the faster back EMF control loop to control the wire feeder motor. This is often preferred because a sufficient amount of data is typically not accumulated during the start-up phase of a welding-type process to allow the tachometer feedback control loop to be accurately interpreted. On the other hand, following the startup phase, the controller switches to using feedback from the tachometer feedback control loop.
However, the specific characteristic and tolerances of motors may vary and result in variations in startup and delivery wire feed speeds (WFS). Specifically, the generalized motor calibration parameters used to control a given motor may not sufficiently match the particular characteristics and tolerances of that motor. For example, generalized motor calibration parameters may be normalized for an entire line of wire feeder motors and not account for the operation of a particular wire feeder motor, such as a replacement motor. As such, generalized motor calibration parameters fail to precisely account for the idiosyncratic efficiencies or variations that nay be present across a line of line feeder motors. As a result, inconsistencies are possible when arc starting. These inaccurate starts can lead to degraded welding processes and result in failed starts, excessive spatter, build-up on the tip of the wire, and generally less accurate welding.
Accordingly, it would be desirable to have a system and method for calibrating wire feeder motor operation. Specifically, it would be desirable to have a system and method to automatically calibrate control of a wire feed motor that considers the particulars of the wire feeder motor to enhance arc starting performance and consistency.